1. Field of the Invention
The present invention relates to electrochemical devices and more particularly to their use for energy storage, in the form of batteries or cells, incorporating electrodes obtained by electrochemical polymerization of a heterocyclic monomer on an electrically conductive support.
Energy storage normally takes place by means of storage batteries, which have a limited number of charging/discharging cycles and large overall dimensions, or cells, which have small overall dimensions, but which cannot be recharged. Thus, it would appear to be difficult to obtain energy storage devices, which have both reduced overall dimensions, which are recyclable and which are reliable over a period of extended use. An increasing need exists for devices which can provide an emergency or standby supply for electronic or electrical systems, which are particularly sensitive, to even brief interruptions in their supply, due e.g. to current interruptions. This is particularly the case with equipment used in the informatics field or members forming telephone exchanges, in order to preserve data stored in memories.
2. Description of the Prior Art
In order to meet these demands, attempts have been made to find devices, which can store a large amount of energy per unit of weight and which accept a large number of charging - discharging cycles. These devices are based on the properties of certain polymers made electrically conductive with the aid of doping agents and which can be used for producing battery electrodes. The advantages of batteries having active polymer elements are a large amount of energy stored per unit of weight and which is roughly twice that of conventional lead batteries, and a high number of charging - discharging cycles. Thus, batteries have been produced using basic polymers, such as polyacetylene, polyphenylene and phenylene polysulphide. However, these polymers have a serious disadvantage, which is the high sensitivity to oxygen. Over a long period, oxygen leads to a deterioration and breaking of the polymer chains. Moreover, particularly in the case of polyacetylene, when producing the electrolyte, it is necessary to use a solvent able to resist electrolysis during charging.